(CNN) -- On a dramatic day at Wimbledon defending champion Serena Williams was dumped out of the tournament, along with her sister Venus and world number one Caroline Wozniacki.

Serena, a 13-time Grand Slam champion, from America, has been out of action for almost a year through injury and health problems and was beaten 6-3 7-6 (8-6) by France's Marion Bartoli in just under two hours on Court No. 1.

It is the earliest Williams -- a former world number one -- has exited a major competition in six years.

On a bad day for the Williams family, Serena's sister Venus, herself a five-time Wimbledon winner, was also dumped out of the competition after losing to Bulgaria's Tsvetana Pironkova for the second successive year.

Wozniacki, who has yet to win a major title despite being ranked number one in the world, was a break up in the deciding set against Dominika Cibulkova, but slumped to a 1-6 7-6 (7-5) 7-5 defeat.

Serena faltered in the opening set, surrendering her serve in the seventh game, and though she rescued three set points to force Bartoli to serve again, the ninth seed held firm.

The second set was a tense affair, both players serving forcefully until Bartoli broke in the 11th game to lead 6-5. Williams, though, responded with an immediate break of her own to force a tie break.

I can only get better. That can potentially be really scary, because I can only go up from here--Serena Williams

Bartoli raced into a commanding lead but Williams dug deep to save four match points before Bartoli finally secured her place in the quarterfinals at the fifth time of asking.

Serena told a news conference: "I think I did really well, just being able to come back and play and win some matches and just really play tough.

"Even though today I lost, I was able to kind of hang in there and play tough. I can only get better. That can potentially be really scary, because I can only go up from here and I can just do so much more."

Bartoli added: "Beating Serena here is like a dream come true. She's been out for a year but she is still one of the greatest champions in the history of women's tennis."

Bartoli will now face German wildcard Sabine Lisicki in the last eight, after she beat Petra Cetkovska of the Czech Republic 7-6 (7-3) 6-1.

Like her sister, Venus also vowed to come back stronger, having returned from five months out with injury to compete at Wimbledon. She insisted her sights were already set on the U.S. Open.

"I look forward to it. I got ready for this tournament so fast. You wouldn't even believe how quick that happened," she told reporters. "With more time, I think I can definitely play better, more matches. Obviously I would love to have peaked here. But, you know, I'm moving on."

Her conqueror, Pironkova, will now face eighth seed Petra Kvitova, from the Czech Republic, after she beat Belgium's Yanina Wickmayer 6-0 6-2.

Wozniacki, from Denmark, told reporters she was frustrated by the manner of her exit to Slovakian opponent Cibulkova, who will face fifth seed Maria Sharapova after the Russian dispatched China's Shuai Peng 6-4 6-2

"It's kind of disappointing because when you're up two-love with a break and have a lot of break points that you don't convert, that's kind of your own fault," she said.

"I had a chance and I usually take it. That's why I am where I am. But today it just didn't go my way. She played well, as well so you just have to give credit to her."

Number four seed Victoria Azarenka, of Belarus,took just 64 minutes to beat Russian Nadia Petrova and she will play unseeded Tamira Paszek, from Austria, who beat Russia's Ksenia Pervak 6-2 2-6 6-3.